1. Field of the Invention
This invention is in the field of power supply and transmittal to a load that is characterized by highly variable peaks and valleys.
The invention is particularly useful in the field of earth scrapers which move along the surface of the earth in order to remove a portion thereof and at the same time an elevating mechanism carries the loosened earth and other materials upwardly into a container.
2. Description of the Prior Art
The patent to Johnson et al. U.S. Pat. No. 3,208,165 discloses an earth scraper with a hydraulically operated conveyor. Johnson discusses the problems that occur in the operation of the conveyor in this type of mechanism. Johnson found that destructive pressure surges of up to 4,000 lbs. per square inch developed each time a flight engaged the loosened dirt. He found that even if he increased the horsepower of the system with a corresponding increase in cost that pressure surges occurred of a destructive nature to the flexible hoses and ultimately to the pump and motor. Johnson proposed to overcome these problems by using a relatively high RPM motor with a gear reduction unit and a relatively heavy flywheel. Using this arrangement Johnson stated that pressure within the system remained substantially constant at 1400 psi with variations of only 200 psi occurring upon engagement of a flight with the loosened dirt. (See Column 5, line 26 to Column 6, line 2).
The teaching of the Johnson patent has been followed through the years up to the present by the industry. Thus, it appears that Johnson has licensed his patent to the major manufacturers of equipment of this nature and that the practice described in his patent has become and remains the standard in the art up to the present time despite the fact that Johnson's system has disadvantages of serious nature. These disadvantages include the relatively high initial cost, and the relatively high maintenance and repair parts problem associated with the high-speed inertia drive system. Thus, if the elevator is stopped suddenly as when the mechanism encounters a large rock, a tree stump, or similar object, the inertia from the flywheel may cause damage to the chain, the flight paddle, other parts of the elevator, or associated mechanism.
It should also be observed that motors of the type manufactured by Rineer Hydraulics, Inc., and used in the combination of the present invention, have been known for many years, the U.S. Pat. No. 3,672,797 for example having been filed Dec. 10, 1969. Such motors have been available on the market for years and the manufacturer has published a description of numerous applications in which such motors are being used, but this does not include the application of the present invention.
Hydraulic drives used in various mechanisms are also disclosed in the U.S. Pat. Nos. to Henry et al. 2,195,308; Twyman 2,301,098; Kopp 2,468,828; Banister et al. 2,658,342; Logus 2,708,800; Amthor et al. 2,894,341; Davis 2,815,047; Allard 3,043,029; Schmidt 3,094,795; Brinkmeyer et al. 3,143,814, Schneider 3,949,553; Yoshioka 3,978,665; and Stieger 4,194,360.